This invention relates to rotating union type coupling devices, and more particularly to sealing assemblies for rotating unions.
Rotating unions are used in applications to couple the outlet of fluid sources to rotating devices. For example, rotating unions are used extensively in the paper processing industry, in high speed drilling and boring transfer operations, high speed machine tool spindles, clutch and brake operations etc.
In high speed drilling apparatus, the rotating unions are used to conduct fluids such as water, or other coolant, from a source to a rotating drill bit. In known rotating unions, a sealing assembly within the rotating union provides the interface between the fixed outlet of the fluid source and the rotating device. The rotor shaft of the rotating union mounts a first seal member for rotation therewith. A second seal member is non-rotatably mounted within the housing of the union. The non-rotating seal member is urged into fluid-tight engagement with the rotating seal face under the force of a bias means, typically a spring arrangement. The coolant fluid which passes through the union lubricates the seal member to minimize wear. In some instances, coolant fluid is not used and thus, the bearing surfaces are unlubricated resulting in increased wear on the seal faces. With extended use, leakage will occur around the seal because of scoring of the seal faces and in particular the seal face of the rotating seal member. Because the rotating seal member is either permanently attached to the rotor, or is integrally formed with the rotor, replacement of a damaged or scored rotating seal member requires replacement of the entire rotor assembly. This is a difficult and expensive operation and requires considerable amount of down time for the apparatus on which the rotating union is used. Thus, it would be desirable to have a rotating union in which wear of the seal assembly is minimized.
Moreover, rotating unions with this type of rotating seal arrangement have been limited to speeds of 15,000 revolutions per minute. It also would be desirable to have a rotating union capable of use at higher speeds than those presently available.